In wireless communications system an identifier is associated with each wireless mobile terminal communicating in the system. The identifier has multiple uses, one use of the identifier is for delivering incoming calls to the wireless mobile terminal, also known as a mobile or a cellular phone. Other uses include, but are not limited to, the registration of the mobile terminal, authentication of the mobile terminal, billing for the mobile terminal, etc. In order to accommodate existing analog and Time Division Multiple Access (TDMA) mobile terminals, Code Division Multiple Access (CDMA) wireless communications systems in the United States can use a fixed 10 digit Mobile Identity Number (MIN) as the identifier.
Typically, mobile subscribers have roamed within their country borders. As wireless networks have grown and travel has increased, many subscribers want to take their mobile terminals with them increasing the need to support international roaming. International Roaming can be defined as allowing mobile subscribers to receive services at any international location away from their home system while roaming in a visited country.
To enable international roaming, the identifier in the mobile terminal is used to determine the location of the Home Location Register for the mobile terminal. With the ever increasing number of mobile terminals, 10 digits are not enough to uniquely identify a mobile terminal for use in all wireless communications systems worldwide. Since the 10 digit MIN is not globally unique, it does not allow for international roaming. Country codes have been used to identify the country of origin, however this only results in the reuse of the 10 digit MIN throughout the world further complicating the expansion of wireless communications.
Presently, many wireless communications systems are capable of using up to 15 digits for the mobile terminal identifier in an identification plan known as International Mobile Station Identity (IMSI). Mobile terminals can utilize one or both of two different types of IMSI identifiers as requested by the Mobile Switching Center (MSC).
One IMSI identifier, called MIN-based IMSI, uses a 15 digit identifier consisting of a MIN Escape Code (MEC) as the upper 5 digits and the MIN as the lower 10 digits. For example, every CDMA mobile terminal currently deployed in the United States has an MEC (and MIN) programmed into it. The other IMSI identifier type is called True-IMSI and it does not contain an MEC and thus is distinct from the MIN-based IMSI identifier. Since not all mobile terminals are capable of using a True-IMSI identifier, existing USA wireless communications systems currently utilize only 10 MIN digits as identifiers. In these systems, mobile terminals can use either the 10 digit MIN identifier or the MIN-based IMSI identifier. The MEC is not sent between systems in either case.
As an example, with CDMA systems, in accordance with CDMA air interface standards IS-95 and IS-2000, a wireless communication system can be configured in only one of two distinct ways. One way is for the wireless communication system to require the mobile terminal to send and receive 10 MIN digits as the identifier. The other way is for the mobile terminal to send and receive MIN-based IMSI digits as the identifier. In order to enable mobile terminals to participate in international roaming, it is desirable for wireless systems throughout the world to migrate to using MIN-based IMSI and/or True-IMSI identifiers.
However, a problem exists with using the MIN-based IMSI identifier. Not all mobile terminals are programmed with the correct MEC from the service provider, therefore these mobile terminals cannot be successfully paged using the MIN-based IMSI identifier. There is no network-wide standard mechanism guaranteeing that the mobile terminal would be paged with a MEC matching the MEC that the mobile terminal has been programmed with. This problem has delayed wireless communications systems' migration to the use of MIN-based IMSI identifiers. It is desirable to provide a way to utilize the MIN-based IMSI identifier despite these existing impediments.